1. Field of the Invention
The present invention relates to a support for underground mining and tunnel construction, comprising an outer tube and an inner tube, which can be pushed into each other in a telescoping manner. A piston acted upon by a hydraulic pressure medium is located in the outer tube. This piston, when acted upon by pressure, acts on the inner tube to cause an extension. The outer tube and the inner tube can be fixed on each other by means of a mechanical locking device.
2. The Prior Art
Such supports are described in the prior art according to WO 94/27029. With the support known according to the state of the art, the mechanical locking device is designed in the form of an annular wedge. This wedge rests against the outer side of the inner tube and which is insertable in the outer tube, the portal side of the outer tube being conically widened for this purpose. The annular wedge is provided with engagement elements on the inside, which dig into the material of the inner tube and deform the inner tube if the forces acting on the support are sufficiently high. It is possible in this way to maintain a relatively high supporting force over a large depth of sinking-in with the mechanical locking device alone. Thus it is not necessary to have to depend on hydraulically generated supporting forces.
A disadvantage of this known support is that the mechanical locking device always first requires a defined depth of sinking-in, or penetration, before it develops its full supporting force. This has the result that after the support has been set and the hydraulic supporting force has been removed, or canceled, there is always a gap in the supporting force. This gap exists until the support has sunk to such an extent that the mechanical locking device is fully supportive.